// One small letter, surrounded by EXACTLY three big bodyguards on each of its sides.
// 一个小写字母,每边都有三个大保镖,而且是仅有

import re

str = open("tmp").read()
print(re.findall(r'[a-z][A-Z][A-Z][A-Z][a-z][A-Z][A-Z][A-Z][a-z]',str1))
//['qIQNlQSLi', 'eOEKiVEYj', 'aZADnMCZq', 'bZUTkLYNg', 'uCNDeHSBj', 'kOIXdKBFh', 'dXJVlGZVm', 'gZAGiLQZx', 'vCJAsACFl', 'qKWGtIDCj']

//linkedlist

// http://www.pythonchallenge.com/pc/def/linkedlist.php to next